1. Field of the Invention
The present invention relates to a method of manufacturing a spacer used in an electron beam generating device, an electron beam generating device using the spacer and an image-forming apparatus.
2. Related Background Art
Up to now, there have been known two sorts of electron beam emitting devices, that is, a hot cathode device and a cold cathode device as an electron source in an electron beam emitting device used in an image-forming apparatus. In the cold cathode device of those cathode devices, there have been known, for example, a surface conduction electron-emitting device, an electric field electron-emitting device (hereinafter referred to as xe2x80x9cFE typexe2x80x9d), a metal/insulating layer/metal electron-emitting device (hereinafter referred to as xe2x80x9cMIM typexe2x80x9d), and the like.
The above surface conduction electron-emitting devices are exemplified by, for example, M. I. Elinson, Radio: Eng. Electron Phys., 10,1290 (1965), and other examples that will be described later. The surface conduction electron-emitting device is so designed as to utilize a phenomenon where a current is allowed to flow to a thin film of a small-area formed on a substrate in parallel with a film surface, to thereby cause electron emission.
As the surface conduction electron-emitting device, there have been reported, in addition to the above-described surface conduction electron-emitting device using an SnO2 thin film by Elinson, a surface conduction electron-emitting device using an Au thin film [G. Dittmer: xe2x80x9cThin Solid Filmsxe2x80x9d, 9,317(1972)], a surface conduction electron-emitting device using an In2O3/SnO2 thin film [M. Hartwell and C. G. Fonstad: xe2x80x9cIEEE Trans. ED Conf.xe2x80x9d, 519(1975)], a surface conduction electron-emitting device using a carbon thin film [Hisashi Araki, et al: Vacuum, volume 26, No. 1, 22 (1983)], and the like.
A typical example of the device structure of those surface conduction electron-emitting devices is exemplified by the above-mentioned device by M. Hartwell, et al as shown in FIG. 23. In this example, reference numeral 3001 denotes a substrate, and 3004 is a plane type electroconductive thin film of an H shape made of metal oxide formed through sputtering. Then, the electroconductive thin film 3004 is subjected to energization processing called xe2x80x9cenergization formingxe2x80x9d which will be described later, to therefore form an electron-emitting portion 3005. Note that, in the figure, an interval L is set to 0.5 to 1 mm, and a width W is set to 0.1 mm. In this example, for the convenience of the drawing, the electron-emitting portion 3005 is indicated by a rectangular. In the center of the electroconductive thin film 3004, but this is schematic and does not faithfully represent the position and configuration of the actual electron-emitting portion.
It is general that in the surface conduction electron-emitting device including the above-mentioned device by M. Hartwell, et al, the electroconductive thin film 3004 is subjected to energization processing called xe2x80x9cenergization formingxe2x80x9d to form the electron-emitting portion 3005. That is, the energization forming is that a constant D.C. voltage or a D.C. voltage that is boosted at a very slow rate such as 1 V/min is applied to the both ends of the electroconductive thin film 3004 to energize the electroconductive thin film 3004 so that the electroconductive thin film 3004 is locally destroyed, deformed or deteriorated, to thereby form the electron-emitting portion 3005 that is in an electrically high-resistant state.
Note that a fissure is formed in a part of the electroconductive thin film 3004 that has been locally destroyed, deformed or deteriorated. Therefore, in the case where an appropriate voltage is applied to the electroconductive thin film 3004 after the energization forming, electron emission is conducted in the vicinity of the fissure.
Also, as the examples of the FE type, there have been known, for example, W. P. Dyke and W. W. Dolan, xe2x80x9cField emissionxe2x80x9d, Advance in Electron Physics, 8, 89(1956), C. A. Spindt, xe2x80x9cPhysical properties of thin-film fie-id emission cathodes with molybdenum conesxe2x80x9d, J. Appl. Phys., 47,5248 (1976), and the like.
As the typical example of the device structure of the FE type, the above-mentioned device by C. A. Spindt, et al is structured as shown in FIG. 24 in which reference numeral 3010 denotes a substrate, 3011 denotes an emitter wiring made of an electroconductive material, 3012 denotes an emitter cone, 3013 denotes an insulating layer, and 3014 denotes a gate electrode. In this device, an appropriate voltage is applied between the emitter cone 3012 and the gate electrode 3014, to thereby conduct the electric field emission from a leading portion of the emitter cone 3012.
Also, as another device structure of the FE type, there is an example in which an emitter and a gate electrode are disposed on a substrate substantially in parallel with a substrate surface which is not of the above-mentioned laminate structure.
Also, as an example of the MIM type, there have been known, for example, C. A. Mead, xe2x80x9cOperation of tunnel-emission Devices, J. Appl, Phys., 32,646 (1961), and the like. A typical example of the MIM type device structure is shown in FIG. 25. In this example, reference numeral 3020 denotes a substrate, 3021 denotes a lower electrode made of metal, 3022 denotes a thin insulating layer having a thickness of about 100 xc3x85, and 3023 denotes an upper electrode made of metal having a thickness of about 80 to 300 xc3x85. The MIM type device is structured such that an appropriate voltage is applied between the upper electrode 3023 and the lower electrode 3021 to conduct the electron emission from the surface of the upper electrode 3023.
The above-described cold cathode device does not require a heater because the device can obtain the electron emission at a low temperature as compared with the hot cathode device. Therefore, the cold cathode device is simple in structure as compared with the hot cathode device and being capable of producing a fine device from the cold cathode device. Also, even if a large number of devices are arranged on the substrate with a high density, it is hard to generate a problem such as heat melting of the substrate. Also, in case of the cold cathode device, there is another advantage in that a response is high in speed, which is different from the hot cathode device (in which the response is low in speed because the device is operated by heating of the heater). For that reason, the applied research of the cold cathode device is increasingly conducted.
For example, the surface conduction electron-emitting device is particularly simple in its structure among the cold cathode devices, and it is easy in manufacture, and therefore has an advantage that a large number of devices can be formed over a large area. Under the circumstance, as disclosed in Japanese Patent Application Laid-Open No. 64-31332 made by the present applicant, a method in which a large number of devices are arranged on a substrate and driven is researched.
Also, as the application of the surface conduction electron-emitting device, there have been researched, for example, an image-forming apparatus such as an image display apparatus or an image recording apparatus, a charge beam source and the like. In particular, as the application to the image display apparatus, as disclosed in Japanese Patent Application Laid-Open No. 2-257551 by the present applicant, Japanese Patent Application Laid-Open No. 4-28137 and U.S. Pat. No. 5,066,883, there has been researched an image display apparatus using the combination of the surface conduction electron-emitting device with a phosphor that emits a light due to the irradiation of an electron beam.
In the image display apparatus using the combination of the surface conduction electron-emitting device with the phosphor; it is expected to have a characteristic superior to the conventional image display apparatus of other types. For example, because the above image display apparatus is of the self-emitting type even as compared with a liquid crystal display apparatus which has been spread in recent years, there are advantages that no back light is required and an angle of visual field is wide.
Also, the method in which a large number of FE type devices are arranged and driven is disclosed in U.S. Pat. No. 4,904,895 by the present applicant. Also, as an example in which the FE type device is applied to the image display apparatus, there has been known a plane type display device, for example, which is reported by R. Meyer, et al [R. Meyer: xe2x80x9cRecent Development on Micro-tips Display at LETIxe2x80x9d, Tech. Digest of 4th Int. Vacuum Micro-electronics Conf., Nagahama, pp. 6 to 9 (1991)]. Also, an example in which a large number of MIM type devices are arranged and applied to the image display apparatus is disclosed in Japanese Patent Application Laid-Open No. 3-55738 by the present applicant.
Among the image-forming apparatus using the above-mentioned electron-emitting devices, attention is paid to a thin plane type display apparatus as the replacement of a CRT display apparatus since the thin plane type display apparatus is space-saving and light in weight.
In the above-described image-forming apparatus, in general, a spacer is arranged between a rear plate and a face plate. The spacer is so designed as to support the rear plate and the face plate so that the rear plate and the face plate withstand an atmospheric pressure, and therefore is demanded to have a sufficient mechanical strength. However, the existence of the spacer must not greatly influence the trajectory of electrons flying between the rear plate and the face plate.
Then, the main cause of giving an influence to the electron trajectory is the charge of the spacer. It is presumed that the spacer charge occurs as a result from a phenomenon in which a part of electrons emitted from the electron source or electrons reflected from the face plate enter the spacer and secondary electrons are emitted from the spacer, or ions that have been ionized due to the collision of electrons are attached onto the surface.
When the spacer is positively charged, the electrons flying in the vicinity of the spacer are attracted to the spacer. Therefore, a distortion occurs in a displayed image in the vicinity of the spacer. Moreover, the influence of the charge becomes more remarkable as an interval between the rear plate and the face plate is larger.
In general, as means for suppressing the charge, electroconductivity is given to the charged surface and a slight current is allowed to flow in the charged surface to remove the electric charges. A method in which this concept is applied to the spacer to coat the spacer surface with tin oxide or the like is disclosed in Japanese Patent Application Laid-Open No. 57-118355. Also, a method in which the spacer surface is coated with PdO glass material is disclosed in Japanese Patent Application Laid-Open No. 3-49135.
Also, the formation of electrodes on the abutment surfaces of the spacer against the face plate and the rear plate makes it possible to prevent the destruction of the spacer due to the connection failure or the current concentration by uniformly applying an electric field to the coating material. This appearance will be described with reference to FIG. 26. In the figure, reference numeral 901 denotes a spacer, 902 denotes a face plate, 903 denotes a rear plate, 904 denotes a higher resistant film coated on the spacer surface, 905 denotes a spacer electrode formed on the spacer, 906 denotes an abutment surface of the spacer at the face plate side, and 907 denotes an abutment surface of the spacer at the rear plate side. The spacer electrode 905 is normally formed by using a method such as sputtering.
Also, Japanese Patent Application Laid-Open No. 2000-164129 discloses a structure in which a plurality of spacer base substances are fixed in such a manner that both side surfaces of each spacer base substance are nipped by a glass fitting jig, and a lower resistant film is formed on an end portion of the spacer base substance that is exposed from the glass fitting jig through sputtering.
A spacer in an electron beam generating device is a very important member, and a method of excellently manufacturing the spacer is demanded at present. Therefore, an object of the present invention is to realize a method of manufacturing an excellent spacer.
In particular, if a film is formed in an undesired region of the spacer, there arises such a problem that an unexpected discharge occurs. Another object of the present invention is to realize a method of manufacturing a spacer that can suppress the formation of a film in an undesired region.
In order to achieve the above objects, according to a first aspect of the present invention, there is provided a method of manufacturing a spacer used in an electron beam generating device, comprising the step of providing a film formation material to a film formation surface of the spacer in a state where a spacer base substance is nipped, wherein the providing step is conducted in a state where the film formation surface is not projected from an end portion of a nipping member for nipping the spacer base substance.
According to this manufacturing method, because the film formation material is provided in a state where the film formation surface is not projected from the end portion of the nipping member, the formation of the film on a side surface of the film formation surface is suppressed.
In particular, in a case where the film to be formed is a film that is high in electroconductivity and forms an electrode, there is the possibility that the formation of the film in the undesired region leads to an undesired discharge. In the case where such a film is formed, the present invention can be particularly preferably applied.
In particular, the present invention can be preferably applied to a structure in which the electron beam generating device includes a first plate where an electron-emitting device is arranged, and a second plate where an acceleration electrode to which an acceleration potential that accelerates electrons emitted from the electron-emitting device is applied.
Also, in particular, in the case where the film formation surface is a surface that faces the first plate or the second plate when the electron beam generating device is structured, the possibility that the formation of an undesired film on the side surface of the film formation surface leads to discharge becomes high. Therefore, the present invention can be preferably applied to this structure. As a structure where a film is formed on a surface that faces the first plate or the second plate when the electron beam generating device is structured, there are, for example, a structure in which a film is formed at a position that is in contact with a wiring (electrode) formed on the first plate, in particular, a wiring that supplies a signal for driving the electron-emitting device, a structure in which a film is formed at a position that is in contact with an acceleration electrode formed on the second plate, and a structure in which a film is formed at a position that is in contact with electrodes (grid electrode, converging electrode) disposed between the first plate and the second plate.
Note that the above-described respective inventions can be preferably applied to a structure in which the plurality of spacer substrates are held in a state where the nipping members are arranged between the respective spacer base substances to give the above material.
Also, it is preferable that the end portion of the nipping member is projected from the film formation surface at the time of providing the material, and corner portions of the projected end portion are rounded. The structure has the advantages that a defect of the nipping member is suppressed, an opening portion structured by a pair of nipping members that nips the spacer base substance has a portion whose opening width in the nipping direction is widened gradually toward the external of the opening from the film formation surface so that the attainment of the material toward the film formation surface becomes excellent.
Note that in the above-described respective inventions, the spacers have electroconductivity and are electrically connected to two different electrodes, and those respective inventions can be particularly preferably applied to a structure in which potentials different from each other are given to the two different electrodes. In the case where the spacer is electrically connected to an accelerating electrode, a grid electrode or an electrode such as a driving wiring of the electron-emitting device, in order that the electric connection is made excellent, and the potential distribution in the spacer is made excellent, it is preferable that the spacer has a film high in electroconductivity. In particular, when the high electroconductivity is given to the entire spacer, the two electrodes to which the spacer is electrically connected are short-circuited, and therefore it is better that the spacer base substance is made of insulating or high resistant material, and a film high in electroconductivity is formed on only a given portion. It is preferable that the film high in the electroconductivity is formed on only the end surface of the spacer (there is no go-around from the end surface to the side surface), and the present invention can be preferably applied to the formation of the above film.
The above-described respective inventions can be particularly preferably applied to a structure in which the spacer base substance is formed of the insulating base substance, and the spacer has the film formed through the giving process and an electroconductive film other than the above film. Note that the giving process may be conducted on the spacer base substance on which the electroconductive film has been formed. Also, the electroconductive film is preferably formed of a film higher in sheet resistance than the film formed through the giving process, and more particularly a higher resistant film.
Also, in the above-described respective inventions, it is preferable that the nipping member has such a shape as to set the end portion of the nipping member to be projected from the film formation surface by 5 xcexcm or more when the material is provided. More preferably, the end portion of the nipping member is projected from the film formation surface by 10 xcexcm or more. The setting of those values makes it possible to surely suppress the formation of the film in an unnecessary region.
Also, in the above-described respective inventions, it is preferable that a length by which the end portion of the nipping member is projected from the film formation surface is set to 10 mm or less. In particular, in the case where the providing of the material is conducted through an electron beam vapor depositing method, it is preferable that the length is set to 8 mm or less.
According to another aspect of the present invention, there is provided an electron beam generating device characterized by providing an electron-emitting device and a spacer manufactured in the methods described in the above-mentioned respective inventions.
Also, according to still another aspect of the present invention, there is provided an image-forming apparatus comprising: an electron-emitting device; an acceleration electrode that accelerates electrons emitted from the electron-emitting device; a phosphor that emits a light by irradiation of the electrons emitted from the electron-emitting device; and a spacer manufactured through the methods described in the above-mentioned respective inventions.
It is possible that a higher resistant film is formed on the surface of the spacer, and positive charges are neutralized to ease the electric charges to prevent the electrons flying in the vicinity of the spacer from being attracted to the spacer. Also, as described above, electrodes are formed on the abutment surfaces of the spacer against the face plate and the rear plate, and an electric field is uniformly applied to the coating material, thereby being capable of preventing the spacer from being destroyed due to a connection failure or a current concentration.
Also, by implementing the present invention, it is suppressed that the electrode of the spacer is protruded to the charged surface due to the degrade of the formation precision at the time of forming the electrode to cause an adverse effect on the electron frajectory so that the situation where the electron beam cannot reach a desired position is suppressed. As a result, the distortion of a display image in the vicinity of the spacer is suppressed, thereby being capable of forming a high-grade image.
Also, as the embodiment modes of the present invention, it is preferable that the above-mentioned higher resistant film is structured by forming a metal oxide film, carbon, an alloy nitride film or the like through any one of a sputtering method, a CVD method, a plasma CVD method and an alkoxide coating method. Also, it is preferable that the spacer electrode is made of a material selected from metal or alloy such as Ni, Cr, Au, Mo, W, Pt, Ti, Al, Cu, Pb or the like having a lower resistance than the above higher resistant film, printing conductor made of metal or metal oxide such as Pd, Ag, Au, Ruxe2x80x94Ag or the like and glass or the like, and transparent conductor such as In2O3xe2x80x94SnO3, and semiconductor material such as polysilicon.
Further, it is preferable that the sheet resistance of the film formed through one or more processes including at least the above providing process is smaller than the sheet resistance of the higher resistant film, and in particular, it is desirable that the former is smaller than the latter by double figures or more.